Among the 14788 women included in this analysis, 11797 (79.8%) had a normal BMI, and 2991 (20.2%) had a BMI ≥ 30 (Fig. 1). Within the group of women with a BMI ≥ 30, 2149 (71.8%) were grade 1 obesity (BMI [30–35[ kg/m²), 628 (20.9%) were grade 2 (BMI [35–40[ kg/m²) and 214 (7.1%) were grade 3 (BMI > 40 kg/m²).
Women with obesity were more often older than 35 compared to women with normal BMI. Women with BMI ≥ 30 had more often history of chronic hypertension, diabetes mellitus and were more often multiparous with a history of previous CS than women with normal BMI. Moreover, women with obesity presented higher medical risk level at the beginning of pregnancy compared to normally weighted women. Complications of pregnancy were more frequent for women with obesity compared to normal weight women with significantly more gestational hypertensive disorders (gestational hypertension and preeclampsia) and gestational diabetes (requiring insulin or simple diet). The maternal obesity group significantly exceeded the total GWG recommended in guidelines. Women with a BMI ≥ 30 displayed more premature birth before 34 weeks of gestation compared to normally weighted women. Induction was more frequent for women with obesity. Moreover, the induction rates were higher for hypertensive gestational pathologies, fetal indication or maternal indication compared to normal weight women.
The overall CS rates were significantly different between the two groups (28.1% for women with obesity versus 14.1% for normal weight women, p < 0.001).
Concerning the distribution into the Robson classification, normal weight women were more often classified in groups 1 (Primiparous, single cephalic presentation, spontaneous labor, ≥ 37 weeks), 2 (Primiparous, single cephalic presentation, ≥ 37 weeks), 3 (Multiparous, single cephalic presentation, spontaneous labor, ≥ 37 weeks), and 6 (Primiparous, single breech presentation) (Table 2). Women with obesity were more often classified in group 4 (Multiparous, single cephalic presentation, ≥ 37 weeks, induced or CS before labor), 5 (Multiparous, single cephalic presentation, history of one or more CS, ≥ 37 weeks, induced or CS before labor), 7 (Multiparous, single breech presentation, including a history of CS) and 10 (Single cephalic presentation, < 37 weeks, including a history of one or more CS), (Table 2). No differences were found in group 8 (Twin pregnancies, including a history of one or more CS) and 9 (Single transverse or oblique lie, including a history of one or more CS) (Table 2).
Table 1: Characteristics of women according to pre-pregnancy BMI
* High medical risk level at the beginning of pregnancy was defined as the presence of one or more of: history of cardiac disease, hypertension, diabetes, venous
thrombosis, pulmonary embolism, Graves’ disease, asthma, homozygous sickle cell anemia, thrombocytopenia, coagulation disorder, a rare or systemic disease,
nephropathy, HIV infection, pre-eclampsia, growth restriction, preterm delivery, fetal death or neonatal death.
** Defined as the occurrence of one or more of the following complications: gestational diabetes, pre-eclampsia, eclampsia, HELLP syndrome,
venous thrombosis, pulmonary embolism, severe sepsis, convulsions, diabetic ketoacidosis, coagulation disorder, cholestasis of pregnancy
*** Excessive total gestational weight gain defined as an intake of more than 9 kg for women with obesity and an intake of more than 15.9 kg for normal weight women.
|
Normal weight
|
Obesity
|
|
|
11797
|
2991
|
p
|
|
N (%)
|
N (%)
|
|
Maternal characteristics
|
|
|
|
Age (years) (mean ± sd)
|
31.82 ± 5.51
|
32.88 ± 5.45
|
< 0.001
|
Age class (years)
|
|
|
< 0.001
|
< 25
|
1343 (11.4)
|
213 (7.1)
|
|
[25–30[
|
3096 (26.2)
|
735 (24.6)
|
|
[30–35[
|
3953 (33.5)
|
974 (32.6)
|
|
≥ 35
|
3405 (28.9)
|
1069 (35.7)
|
|
Multiparous women
|
6639 (56.3)
|
2280 (76.2)
|
< 0.001
|
Previous cesarean delivery
|
|
|
< 0.001
|
1
|
1082 (9.2)
|
561 (18.8)
|
|
≥ 2
|
220 (1.9)
|
246 (8.2)
|
|
Body mass index before pregnancy (kg/m²) (mean ± sd)
|
21.48 ± 1.66
|
33.47 ± 3.54
|
< 0.001
|
Smoker
|
1585 (13.7)
|
307 (10.6)
|
< 0.001
|
Diabetes mellitus
|
94 (0.8)
|
113 (3.8)
|
< 0.001
|
Chronic hypertension
|
116 (1.0)
|
163 (5.4)
|
< 0.001
|
Bariatric surgery
|
|
|
< 0.001
|
Bypass
|
30 (0.3)
|
36 (1.2)
|
|
Sleeve gastrectomy
|
28 (0.2)
|
56 (1.9)
|
|
Gastric band
|
14 (0.1)
|
68 (2.3)
|
|
Hight medical risk level at the beginning of pregnancy*
|
1880 (15.9)
|
878 (29.4)
|
< 0.001
|
Pregnancy characteristics
|
|
|
|
Complications of pregnancy**
|
1042 (8.8)
|
870 (29.1)
|
< 0.001
|
Twin pregnancy
|
481 (4.1)
|
105 (3.5)
|
0.172
|
Fetal presentation
|
|
|
0.019
|
Cephalic
|
11117 (94.2)
|
2782 (93.0)
|
|
Breech
|
659 (5.6)
|
198 (6.6)
|
|
Transverse
|
20 (0.2)
|
10 (0.3)
|
|
Weight intake during pregnancy (mean ± sd)
|
12.24 ± 5.28
|
7.74 ± 7.00
|
< 0.001
|
Excessive total GWG***
|
2691 (23.7)
|
1308 (45.7)
|
< 0.001
|
Gestational diabetes requiring insulin
|
162 (1.4)
|
295 (9.9)
|
< 0.001
|
Gestational diabetes without insulin
|
477 (4.0)
|
361 (12.1)
|
< 0.001
|
In utero transfer
|
198 (1.7)
|
57 (1.9)
|
0.439
|
Premature rupture of membranes
|
163 (1.4)
|
76 (2.5)
|
< 0.001
|
Preterm labor
|
725 (6.1)
|
158 (5.3)
|
0.083
|
Gestational hypertension
|
80 (0.7)
|
105 (3.5)
|
< 0.001
|
Preeclampsia
|
233 (2.0)
|
151 (5.0)
|
< 0.001
|
HELLP syndrome
|
15 (0.1)
|
8 (0.3)
|
0.081
|
Eclampsia
|
2 (0.0)
|
1 (0.0)
|
0.57
|
Suspected small for gestational age
|
254 (2.2)
|
40 (1.3)
|
0.005
|
Cholestasis
|
126 (1.1)
|
40 (1.3)
|
0.25
|
Deep vein thrombosis during pregnancy
|
9 (0.1)
|
3 (0.1)
|
0.958
|
Pulmonary embolism during pregnancy
|
1 (0.0)
|
3 (0.1)
|
0.035
|
Delivery characteristics
|
|
|
|
Gestational age at delivery
|
|
|
|
< 28
|
70 (0.6)
|
33 (1.1)
|
0.004
|
[28–34[
|
304 (2.6)
|
106 (3.5)
|
0.004
|
[34–37[
|
679 (5.8)
|
186 (6.2)
|
0.35
|
[37–41[
|
8634 (73.2)
|
2124 (71.0)
|
0.02
|
≥41
|
2110 (17.9)
|
542 (18.1)
|
0.78
|
Induction
|
2515 (21.3)
|
870 (29.1)
|
< 0.001
|
Induction indication
|
|
|
< 0.001
|
Fetal
|
826 (7.0)
|
258 (8.6)
|
0.003
|
Maternal
|
155 (1.3)
|
82 (2.7)
|
< 0.001
|
Premature rupture of membranes
|
857 (7.3)
|
251 (8.4)
|
0.04
|
Post term
|
404 (3.4)
|
131 (4.4)
|
0.01
|
Gestational hypertension or preeclampsia
|
246 (2.1)
|
146 (4.9)
|
< 0.001
|
Non medical
|
27 (0.2)
|
2 (0.1)
|
0.11
|
Delivery mode
|
|
|
< 0.001
|
Vaginal delivery
|
10130 (85.9)
|
2150 (71.9)
|
|
Cesarean delivery
|
1667 (14.1)
|
841 (28.1)
|
|
Cesarean delivery profiles between the normal weight and the maternal obesity groups are presented in Table 2. Within each group of the Robson classification women with obesity delivered more often by CS than normal weight women (Table 2).
The Robson category 5 (Multiparous, single cephalic presentation, history of one or more CS, ≥ 37 weeks) contributed the most to the difference in cesarean rates between normally weighted women and women with obesity with a difference in absolute contribution of 8.4%. This figure is due to a bigger size of the group and a higher CS rate for women with obesity. Robson group 5 was then divided into two subgroups: a single history of cesarean delivery (group 5a) and a history of more than one cesarean delivery (category 5b). The overall cesarean rate in group 5a was increased for the women with obesity group compared to the normal weight group: 32.9 and 22.4% respectively (p < 0.001). The results were similar when we distinguished CS before labor (6.8% for women with obesity versus 4.8% for normal weight group, p < 0.001, Table S1) and CS during labor (26.1% for women with obesity versus 17.5% for normal weight group, p < 0.001, Table S1). Women with obesity had more cesarean section for abnormal fetal heart rate (13,7% versus 9.4% for normal weight women, p = 0.02) and arrest of labor (13.2% versus 8.3% for normal weight women, p = 0.005). Induction rates were higher for women with obesity in group 5a (33,8% versus 22% for normally weighted women, p < 0.001) especially for fetal, maternal and gestational hypertensive disorders. After adjustment, the association between maternal pre-pregnancy BMI and cesarean delivery before labor in group 5a was not statistically significant (aOR = 1.26 CI: [0.76–2.08], adjustment for maternal age, high medical risk level at the beginning of pregnancy, pregnancy complications Table S2), whereas the association between maternal pre-pregnancy BMI and cesarean delivery during labor in group 5a was statistically significant (aOR = 1.43, 95% CI: [1.07–1.9], adjustment for maternal age, high medical risk level at the beginning of pregnancy, pregnancy complication and induction, Table S3).
Neonates of women with obesity compared with the ones of normally weighted women had more often fetal macrosomia, presented more Apgar score < 7 at 5 minutes and more transfers in NICU or neonatal reanimation (Table 3).
Table 2: Cesarean delivery profiles according to maternal pre-pregnancy BMI using Robson classification.
*Group 1: primiparous, single cephalic presentation, spontaneous labor, ≥ 37 weeks.
*Group 2: primiparous, single cephalic presentation, ≥ 37 weeks.
*Group 2a: primiparous, single cephalic presentation, ≥ 37 weeks, induction.
*Group 2b: primiparous, single cephalic presentation, ≥ 37 weeks, CS before labor.
*Group 3: multiparous, single cephalic presentation, spontaneous labor, ≥ 37 weeks.
*Group 4: multiparous, single cephalic presentation, ≥ 37 weeks.
*Group 4a: multiparous, single cephalic presentation, ≥ 37 weeks, induction.
*Group 4b: multiparous, single cephalic presentation, ≥ 37 weeks, CS before labor.
*Group 5: multiparous, single cephalic presentation, history of one or more CS, ≥ 37 weeks.
*Group 5a: multiparous, single cephalic presentation, history of one or more CS, ≥ 37 weeks, history of one CS.
*Group 5b: multiparous, single cephalic presentation, history of one or more CS, ≥ 37 weeks, history of more than one CS
*Group 6: primiparous, single breech presentation
*Group 7: multiparous, single breech presentation, including a history of CS
*Group 8: twin pregnancies, including a history of one or more CS
*Group 9: single transverse or oblique lie, including a history of one or more CS
*Group 10: single cephalic presentation, < 37 weeks, including a history of one or more CS
|
Number of CS/number of women in each category
|
Size of each category (%) (number of women in each category divided by the total number of women)
|
CD rate in each category (%) (number of cesarean deliveries in the category divided by the number of women in the category)
|
CD distribution (%) (number of cesarean deliveries in the category divided by the total number of CD)
|
Contribution of each category (%) (number of cesarean deliveries in each category divided by the total number of women)
|
|
Obese
|
Normal weight
|
Obese
|
Normal weight
|
dif
|
Obese
|
Normal weight
|
dif
|
Obese
|
Normal weight
|
dif
|
Obese
|
Normal weight
|
dif
|
Robson group*
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
group 1
|
66/346
|
281/3226
|
11.6
|
27.3
|
-15.7
|
19.1
|
8.7
|
10.4
|
7.8
|
16.9
|
-9.1
|
2.20
|
2.38
|
-0.17
|
group 2
|
99/240
|
288/1130
|
8
|
9.6
|
-1.6
|
41.2
|
25.5
|
15.7
|
11.8
|
17.2
|
-5.4
|
3.30
|
2.53
|
0.78
|
group 2a
|
83/224
|
234/1076
|
7.5
|
9.1
|
-1.6
|
37.1
|
21.7
|
15.4
|
9.9
|
14
|
-4.1
|
2.77
|
1.98
|
0.79
|
group 2b
|
16/16
|
54/54
|
0.5
|
0.5
|
0
|
100
|
100
|
0
|
1.9
|
3.2
|
-1.3
|
0.53
|
0.46
|
0.08
|
group 3
|
43/910
|
68/3943
|
30.4
|
33.4
|
-3
|
4.7
|
1.7
|
3
|
5.1
|
4.1
|
1
|
1.44
|
0.58
|
0.86
|
group 4
|
52/351
|
51/735
|
11.8
|
6.3
|
5.5
|
14.8
|
6.9
|
7.9
|
6.2
|
3.1
|
3.1
|
1.74
|
0.43
|
1.30
|
group 4a
|
41/340
|
31/715
|
11.4
|
6.1
|
5.3
|
12.1
|
4.3
|
7.8
|
4.9
|
1.9
|
3
|
1.37
|
0.26
|
1.11
|
group 4b
|
11/11
|
20/20
|
0.4
|
0.2
|
0.2
|
100
|
100
|
0
|
1.3
|
1.2
|
0.1
|
0.37
|
0.17
|
0.20
|
group 5
|
342/659
|
360/1074
|
22
|
9.1
|
12.9
|
51.9
|
33.5
|
18.4
|
40.7
|
21.6
|
19.1
|
11.43
|
3.05
|
8.38
|
group 5a
|
154/468
|
204/912
|
15.6
|
7.7
|
7.9
|
32.9
|
22.4
|
10.5
|
18.3
|
12.2
|
6.1
|
5.15
|
1.73
|
3.42
|
group 5b
|
188/191
|
156/162
|
6.4
|
1.4
|
5
|
98.4
|
96.3
|
2.1
|
22.4
|
9.4
|
13
|
6.28
|
1.32
|
4.96
|
group 6
|
17/29
|
150/272
|
1
|
2.3
|
-1.3
|
58.6
|
55.1
|
3.5
|
2
|
9
|
-7
|
0.57
|
1.27
|
-0.70
|
group 7
|
92/136
|
134/266
|
4.5
|
2.3
|
2.2
|
67.6
|
50.4
|
17.2
|
10.9
|
8
|
2.9
|
3.07
|
1.13
|
1.94
|
group 8
|
44/104
|
160/478
|
3.5
|
4.1
|
-0.6
|
42.3
|
33.5
|
8.8
|
5.2
|
9.6
|
-4.4
|
1.47
|
1.35
|
0.11
|
group 9
|
10/10
|
20/20
|
0.3
|
0.2
|
0.1
|
100
|
100
|
0
|
1.2
|
1.2
|
0
|
0.33
|
0.17
|
0.16
|
group 10
|
76/206
|
155/653
|
6.9
|
5.5
|
1.4
|
36.9
|
23.7
|
13.2
|
9
|
9.3
|
-0.3
|
2.54
|
1.31
|
1.23
|
Table 3: neonatal outcomes of singleton pregnancies according to maternal pre-pregnancy BMI
|
Normal weight
|
Obesity
|
p
|
|
N = 11316
|
N = 2886
|
|
|
N (%)
|
N (%)
|
|
Birth weight (grams) (mean ± sd)
|
3233 ± 568
|
3313 ± 688
|
< 0.001
|
Birth weight (grams)
|
|
|
< 0.001
|
[2500–3800[
|
8981 (79.4)
|
2011 (69.7)
|
|
< 2500
|
850 (7.5)
|
252 (8.7)
|
|
> 3800
|
1485 (13.1)
|
623 (21.6)
|
|
pH at ombilical cord
|
|
|
< 0.001
|
pH < 7
|
36 (0.3)
|
19 (0.7)
|
|
pH [7–7, 1]
|
150 (1.4)
|
64 (2.3)
|
|
pH ]7.1–7.2[
|
709 (6.4)
|
179 (6.3)
|
|
pH ≥ 7.2
|
10185 (91.9)
|
2558 (90.7)
|
|
Apgar score < 7 at 5 minutes
|
132 (1.2)
|
68 (2.4)
|
< 0.001
|
Neonatal transfer
|
|
|
< 0.001
|
Neonatal reanimation unit
|
443 (3.9)
|
175 (6.1)
|
|
Intensive care unit
|
622 (5.5)
|
223 (7.8)
|
|
Other specialized services
|
65 (0.6)
|
20 (0.7)
|
|